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Interferometric Imaging of Titan's HC3N, H13CCCN, and HCCC15N

Research output: Contribution to journalArticle

Original languageEnglish
Article numberL15
Number of pages6
JournalAstrophysical Journal Letters
Issue number1
Early online date23 May 2018
DateAccepted/In press - 9 May 2018
DateE-pub ahead of print - 23 May 2018
DatePublished (current) - 23 May 2018


We present the first maps of cyanoacetylene isotopologues in Titan's atmosphere, including H13CCCN and HCCC15N, detected in the 0.9 mm band using the Atacama Large Millimeter/submillimeter array (ALMA) around the time of Titan's (southern winter) solstice in 2017 May. The first high-resolution map of HC3N in its v 7 = 1 vibrationally excited state is also presented, revealing a unique snapshot of the global HC3N distribution, free from the strong optical depth effects that adversely impact the ground-state (v = 0) map. The HC3N emission is found to be strongly enhanced over Titan's south pole (by a factor of 5.7 compared to the north pole), consistent with rapid photochemical loss of HC3N from the summer hemisphere combined with production and transport to the winter pole since the 2015 April ALMA observations. The H13CCCN/HCCC15N flux ratio is derived at the southern HC3N peak, and implies an HC3N/HCCC15N ratio of 67 ± 14. This represents a significant enrichment in 15N compared with Titan's main molecular nitrogen reservoir, which has a 14N/15N ratio of 167, and confirms the importance of photochemistry in determining the nitrogen isotopic ratio in Titan's organic inventory.

    Research areas

  • planets and satellites: atmospheres, planets and satellites: individual (Titan), submillimeter: planetary systems, techniques: imaging spectroscopy, techniques: interferometric

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